( 1. 中南大学 化学化工学院, 长沙 410083;
2. 深圳大学 应用化学系， 深圳 518060)
摘 要: 采用石英晶体微天平现场技术研究了Hg(Ⅱ)离子在纳米TiO2表面的吸附及光化学还原过程。 结果表明： Hg(Ⅱ)离子借助于纳米TiO2表面羟基发生吸附， 吸附平衡常数约为3.9×105 L/mol， 且 Hg(Ⅱ)离子的吸附量受溶液的pH值、 浓度和共存阴离子的影响； 在pH值为4的HgCl2溶液中， Hg(Ⅱ)离子在纳米TiO2上的饱和吸附量约为0.85 mmol/g; 在UV光照射下， 初始阶段TiO2表面水光解产生的质子可使吸附的 Hg(Ⅱ)离子从TiO2表面脱附下来， 而且Hg(Ⅱ)浓度和pH值越大, 脱附现象越明显； 随后Hg(Ⅱ)光还原沉积逐渐占主导地位， 且光沉积速率受Hg(Ⅱ)浓度、 溶液pH值和有机物加入的影响。
关键字: 纳米TiO2； 吸附； 光化学还原； 石英晶体微天平
（ 1. School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China;
2. Department of Applied Chemistry, Shenzhen University,
Shenzhen 518060, China）
Abstract: In-situ technique of quartz crystal microbalance (QCM) was used to investigate the adsorption and the photochemical reduction process of Hg(Ⅱ) at the surface of nanocrystalline TiO2. The results show the Hg(Ⅱ) is adsorbed onto the surface of nanocrystalline TiO2 by hydroxyl groups, and the adsorption equilibrium constant is about 3.9×105 L/mol based on the pseudo-first-order kinetic model. The adsorption amount of Hg(Ⅱ) at the surface of TiO2 is affected by pH value, concentration of Hg(Ⅱ) and coexisting anions, and the saturated adsorption amount of Hg(Ⅱ) is approximately 0.85 mmol/g at pH of 4. During the initial stage of UV illumination, the protons produced in photodegradative reactions of water can cause the desorption of adsorbed Hg(Ⅱ) from the surface of TiO2. The degree of desorption increases with the increase of both the concentration of Hg(Ⅱ) and pH value of solution. Then, the photochemical deposit reaction of Hg from the solution strengths and the rate of Hg photodeposition are influenced by the concentration of Hg(Ⅱ), pH value and added organics.
Key words: nano titanium dioxide; adsorption; photoreduction; quartz crystal microbalance
